Re: Roll forward using Archive Logs

Maxim Demenko wrote:
> Chintu schrieb:
> > docs -> Backup and Recovery Concepts pg 48 says
> > " crash or instance reecovery use only online redo logs and never
> > require use of archive log "
> >
> > My question is how will it rollforward if the redo for pending
> > transaction are in archive logs ???
> >
> > Thanks
> >
> > Chintu
> >
>
> Redo can be archived only after the log switch, switch cause a
> checkpoint which in turn force dbwr to write all dirty buffers to the
> datafiles. By doing so oracle synchronize the versions of data blocks in
> cache and in datafiles. This means, if you do an update emp set
> ename='ELLISON' where ename = 'KING' and do a logswitch, then
> corresponding block in datafile will contain the version with 'ELLISON'
> ( if not overwritten by more recent change ). So, if you do rollforward,
> you don't need to start with an very old version of block ( information
> of which may be contained in archived log), but with almost recent
> version of it. In other words, Oracle makes it sure, that changes, which
> should be applied to the data block from datafile to bring it up on the
> most recent state, is contained in online redo logs.
>
> I would also recommend to read an excellent post from Tanel Põder, which
> relates to the question you are interested in
> http://www.freelists.org/archives/oracle-l/12-2005/msg00537.html
>
> Best regards
>
> Maxim

Thanks to all. I think I should have thought for a while and then posted. It was just basic concepts. Thanks again Received on Tue May 16 2006 - 04:09:05 CDT